Transverse fan assemblies are well known in the art. Transverse or cross-flow fans typically include axially spaced disk-like members that support a plurality of elongated fan blades in a cylindrical pattern or army. As many as thirty-six fan blades may be arranged in a cylindrical arrangement.
Recently, cross-flow fans have been embodied for use with agricultural combines. A typical agricultural combine includes a crop header apparatus which reaps planted grain stalks and then feeds the grain stalks to a threshing apparatus arranged within a body of the combine. The threshing apparatus functions to separate groin from material other than grain. The grain falls through openings in the threshing apparatus. Essentially, most materials other than grain pass toward and are ultimately directed out a rear end of the combine.
While the threshing apparatus acts to separate a substantial portion of the crop or grain from material other than grain, some chaff or straw is directed out through the openings in the threshing apparatus along with the grain, and a further cleaning or separating action is required. Further separation is normally achieved in a cleaning section of the combine.
A typical combine cleaning section includes oscillating cleaning sieves. The cleaning sieves are located below the threshing apparatus to receive the grain and other materials expelled from the threshing apparatus. The oscillation of the sieves arranges the material in a crop mat or veil on top of the sieves. By forcing a stream of air upwardly through the sieves, chaff, straw and other lighter material in the crop material mat is separated from heavier grain, and the chaff, straw and other lighter material is directed out through the rear end of the combine by the air flow. The heavier seeds or grain fall through the sieves for collection.
With the increased power and output demands of modem agricultural combines, cleaning section capacity has become a limiting factor to performance of the combine. The most readily achieved method of increasing combine efficiency is by increasing the size of the cleaning area and the sieves to spread the crop materials across a wider area and in a thinner crop mat or veil.
Increasing the width of the cleaning area also means increasing the width of the combine. Because of the width of fence openings and the size of barn doors and the like, increasing the width of a combine beyond current limits presents significant problems involving everyday combine operation.
Transverse blower fans are particularly useful in combination with combine cleaning sections because they conserve space and produce a wide stream of air that is directed upwardly toward the cleaning sieves of the combine cleaning section. Because the fan in an agricultural combine is disposed closer to the ground over which the combine moves, the fan blades would normally be exposed to engage rocks and other debris. As will be appreciated, rocks and other debris commonly found in fields can be detrimental to the normal high speed rotational operation of the fan blades. Moreover, broken and/or bent fan blades affect fan performance and thereby efficiency of the combine. Accordingly, the fan on a combine is normally protected by a fan wrapper or air plenum. The fan is rotatably mounted within an inner chamber of the air plenum to drive air between an air inlet and an air outlet.
While having a relatively wide output of air, cross-flow or transverse fans are known to have poor "end effect" air characteristics. For purpose of this description "end effect" air flow means the amount of air flow provided at opposite ends of the fan during fan rotation and as compared to relative output air flow along other lengthwise portions of the fan. The affected area can be measured inwardly from opposite ends of the fan and is generally equal to about the radius of the fan.
As will be appreciated, poor end effect air output means that those crop materials disposed toward opposite sides of the sieves does not benefit from the same air flow characteristics as those crop materials disposed toward the lateral center of the sieve. Thus, the effective cleaning area of the combine is significantly reduced by end air effects at opposite ends of the fan. The adverse performance of the fan at opposite ends thereof can be even more detrimental when the combine is operated on a hillside or in other fields having uneven terrain and wherein the frame is tilted such that crop material gravitates toward a lower side of the cleaning sieve. Of course, wrapping an air plenum about the fan exacerbates the air flow problem.
Thus, there is a need and a desire for a transverse fan assembly having a substantially even output of air flow across the entirety thereof with little or no end air effects associated therewith.